Showing papers by "Masahiro Murakami published in 2012"

Synthesis of α-Amino Ketones from Terminal Alkynes via Rhodium-Catalyzed Denitrogenative Hydration of N-Sulfonyl-1,2,3-triazoles

Abstract: N-Sulfonyl-1,2,3-triazoles react with water in the presence of a rhodium catalyst to produce α-amino ketones in high yield. An intermediary α-imino rhodium(II) carbenoid undergoes insertion into the O–H bond of water. This transformation formally achieves 1,2-aminohydroxylation of terminal alkynes in a regioselective fashion when combined with the copper(I)-catalyzed 1,3-dipolar cycloaddition with N-sulfonyl azides.

Synthesis of enaminones by rhodium-catalyzed denitrogenative rearrangement of 1-(N-sulfonyl-1,2,3-triazol-4-yl)alkanols.

Abstract: Enaminones are synthesized by the rhodium(II)-catalyzed denitrogenative rearrangement reaction of 1-(N-sulfonyl-1,2,3-triazol-4-yl)alkanols, which are readily prepared from propargylic alcohols and N-sulfonyl azides. Intramolecular 1,2-hydride (or -alkyl) migration occurs with an intermediary α-imino rhodium(II) carbenoid species generated through denitrogenation of the 1,2,3-triazol-4-yl moiety. The resulting enaminones is converted into various heterocycles with replacement of the N-sulfonyl group.

Atom‐ and Step‐Economical Pathway to Chiral Benzobicyclo[2.2.2]octenones through Carbon–Carbon Bond Cleavage

Abstract: It has become an imperative issue to improve the step as well as atom economy of organic synthesis. A highly atomeconomical method to construct carbon frameworks could arise if an unsaturated organic functionality is directly inserted into a carbon–carbon single bond. Such an insertion reaction also dispenses with functional group manipulations to significantly reduce the steps required for construction of a particular organic skeleton. A class of benzobicyclo[2.2.2]octene derivatives (1–3 ; Figure 1)) is known to possess a variety of biological activities. For example, benzobicyclo[2.2.2]octenols 1 act

Rhodium-Catalyzed Ring Opening of Benzocyclobutenols with Site-Selectivity Complementary to Thermal Ring Opening

Abstract: A rhodium catalyst induced ring opening of benzocyclobutenols with selective cleavage of the C(sp2)–C(sp3) bond adjacent to the hydroxyl group. The site-selectivity markedly contrasted with that of their thermal ring-opening reaction. The rhodium-catalyzed ring opening led to the development of a new alkyne insertion reaction constructing a dihydronaphthalene framework.

Solar-Driven Incorporation of Carbon Dioxide into α-Amino Ketones†

Abstract: The recent manifestation of the potential risk inherent to nuclear technologies has incited a strong demand for exploration of innovative means to exploit energy from natural sources, thus increasing the need for research on sustainable energy in many scientific fields. Chemists can contribute by developing chemical systems to utilize solar light, which is undoubtedly the best source of sustainable energy available on the planet. Another imperative issue is the establishment of carbon-neutral systems. One synthetic approach to this issue is the incorporation of CO2 into organic compounds as a chemical feedstock. High-energy compounds suit energetically low CO2 as the reaction partner. Under these circumstances, it presents a significant challenge to simultaneously tackle the two issues mentioned above. Thus, we tried to develop a reaction that is promoted by solar light and utilizes CO2 as a chemical feedstock (Figure 1).

Enhancement of affinity in molecular recognition via hydrogen bonds by POSS-core dendrimer and its application for selective complex formation between guanosine triphosphate and 1,8-naphthyridine derivatives

Abstract: We report that a polyhedral oligomeric silsesquioxane (POSS) core in a dendrimer can enhance the affinity of the molecular recognition via hydrogen bonds between 1,8-naphthyridine and guanosine nucleotides. The complexation of the naphthyridine ligands with a series of guanosine nucleotides was investigated, and it is shown that the POSS core should play a significant role in the stabilization of the complexes via hydrogen bonds. Finally, we demonstrate that the 1,8-naphthyridine ligand can selectively recognize guanosine triphosphate by assisting with the POSS-core dendrimer.

Synthesis of AzaaromaticBorane Intramolecular Complexes by Palladium-Catalyzed Reaction of Azaaromatic Halides with Alkynyl(triaryl)borates

Abstract: A diversity-oriented method to synthesize (E)-azastilbenes having an intramolecular BN coordination bond from alkynyl(triaryl)borates and azaaromatic halides is described. The obtained π-conjugated compounds exhibit an intense blue fluorescence and a high electron affinity, indicating their potential to be used as n-type light-emitting materials.

Synthesis of α‐Amino Ketones from Terminal Alkynes via Rhodium‐Catalyzed Denitrogenative Hydration of N‐Sulfonyl‐1,2,3‐triazoles.

Abstract: N-Sulfonyl-1,2,3-triazoles react with water in the presence of a rhodium catalyst to produce α-amino ketones in high yield. An intermediary α-imino rhodium(II) carbenoid undergoes insertion into the O–H bond of water. This transformation formally achieves 1,2-aminohydroxylation of terminal alkynes in a regioselective fashion when combined with the copper(I)-catalyzed 1,3-dipolar cycloaddition with N-sulfonyl azides.

Synthesis of (1H)-Isochromen-1-imines by Nickel-catalyzed Reaction of 2-Iodobenzamides with Alkynes

Abstract: 2-Iodobenzamides reacted with alkynes in the presence of a nickel(0)/P(4-ClC6H4)3 catalyst to produce substituted (1H)-isochromen-1-imines. The reaction proceeded through the formation of an oxanic...

Rhodium-Catalyzed Reaction of 1-Alkenylboronates with Aldehydes Leading to Allylation Products.

Abstract: Alkenylboronates are used as allylating agents in the reaction with aldehydes in the presence of a cationic rhodium(I)/dppm catalyst to give anti-configured homoallylic alcohols with high diastereoselectivity.

Synthesis of Enantiopure Dehydropiperidinones from α-Amino Acids and Alkynes via Azetidin-3-ones.

Abstract: The Ni-catalyzed treatment of the azetidinones allows a new access to optically active dehydropiperidinones.

Atom‐ and Step‐Economical Pathway to Chiral Benzobicyclo[2.2.2]octenones Through Carbon—Carbon Bond Cleavage.

Abstract: The asymmetric intramolecular alkene insertion reaction of 3-(2-styryl)cyclobutanones is efficiently catalyzed by Ni(cod)2 in the presence of PAM.

Synthesis of 3,3-Disubstituted α-Tetralones by Rhodium-Catalyzed Reaction of 1-(2-Haloaryl)cyclobutanols.

Abstract: The asymmetric version of the title reaction affords chiral α-tetralones bearing an asymmetric quaternary carbon at the 3-position.

Synthesis of Phenanthridinones and Phenanthridine Derivatives Through Palladium-Catalyzed Oxidative C—H Coupling of Benzanilides.

Abstract: Under the presented reaction conditions for the synthesis of the phenanthridinones (II) bromo and cyano substituents are not tolerated.